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help!why not use Rx as loop counter?

huang faqian

I have a problem. I write a function in another c source file not main file, in this function nothing do, and I declare the function as extern. In main function I invoke it 200 times. However, the compiler does not use registerbank as counter. Why?

extern void func1(void);

void func2(void)
{
        unsigned char data i;
        for(i=200;i;i--);
}

main()
{
        unsigned char data i,j;
        for(i=200;i;i--)        // store i in 0x08
        {
                func1();
        }
        for(j=200;j;j--)        // store j in R6
        {
                func2();
        }
}
the assembly code:
C:0x0003    7508C8   MOV      0x08,#TMR2CN(0xC8)
    19:         {
    20:                 func1();
C:0x0006    120025   LCALL    func1(C:0025)
    21:         }
C:0x0009    D508FA   DJNZ     0x08,C:0006
    22:         for(j=200;j;j--)
C:0x000C    7EC8     MOV      R6,#TMR2CN(0xC8)
    23:         {
    24:                 func2();
C:0x000E    120020   LCALL    func2(C:0020)
    25:         }
C:0x0011    DEFB     DJNZ     R6,C:000E

Parents
  • 0

    "However, the compiler does not use registerbank as counter."

    I assume you're asking why (for example) R7 isn't being used as your counter?

    Probably something to do with the fact that you've explicitly told the compiler to store the variables in data space.

Reply
  • 0

    "However, the compiler does not use registerbank as counter."

    I assume you're asking why (for example) R7 isn't being used as your counter?

    Probably something to do with the fact that you've explicitly told the compiler to store the variables in data space.

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